Activity standardisation of 161Tb.

161Tb, which emits low-energy β−- and γ-particles in addition to conversion and Auger electrons, has aroused increased interest for medical imaging and therapy. To support the use of this radionuclide, a161Tb solution was standardised using the β-γ coincidence technique, as well as the TDCR method. The solution had 4.5·10−3% of 160Tb impurities. Primary coincidence measurements, with plastic or liquid scintillators for beta detection, were carried out using both analogue and digital electronics. TDCR measurements using defocusing, grey filtering and quenching for varying the efficiency were also made. Monte Carlo calculations were used to compute the detection efficiency. The coincidence measurements with analogue electronics and the TDCR show a good consistency, and are compatible with the digital coincidence results within uncertainties. An ampoule of this solution was submitted to the BIPM as a contribution to the international reference system. • 161Tb has aroused increased interest recently for medical imaging and therapy. • 161Tb was standardised using the β(PS,LS)-γ(CeBr 3) coincidence techniques. • 161Tb was also standardised with the TDCR method using MC electron spectra. • Coincidence results are consistent with TDCR measurements. • An ampoule of the solution was submitted to the International Reference System. [ABSTRACT FROM AUTHOR]